It is a general practice in the design of vacuum furnaces to include heating elements which are located within a structure designated as a hot zone assembly. The hot zone assembly holds the heat generated by the heating elements. It is very often the practice that when the heat treating of a workpiece or workpieces (which has or have been located in the hot zone assembly), is complete, the hot zone assembly is filled with an inert gas, such as nitrogen, and the heat treated pieces are cooled or quenched. As described in U.S. Pat. No. 4,395,832, a plenum can be formed around the outside of the hot zone assembly to assist in the quenching process. The quenching gas is passed into the plenum and through nozzles therefrom which are located between the plenum and the inside section of the hot zone assembly. In the prior art such nozzles have been fabricated from molybdenum since they are subjected to great heat and to repeated hot-cold cycles. I have determined, however, that molybdenum reacts to certain vapors such as nickel chromium vapor. When molybdenum nozzles are subjected to such vapors, the nozzles tend to fuse with the nuts or threaded members, into which they are threaded for support purposes. In addition, certain vapors cause the molybdenum nozzles to shrivel to a certain extent. I have found that: graphite material can be machined into threaded nozzles, if it is carefully done; graphite nozzles can be threaded into the holding pieces (such as nuts welded to the outside wall); and graphite material is not reactive with the vapors which occur in response to elevated temperatures and vacuum conditions and are generally found in a vacuum furnace. Accordingly, the graphite nozzles do not fuse with the holding means and remain removable.